Conventionally, with a view to detecting a passenger approaching a doorway of an elevator, there is proposed a door device for an elevator which has a light emitter provided on one of longitudinal frames constituting part of a three-side frame and a light receiver provided on the other longitudinal frame. Light from the light emitter is received by the light receiver. When the passenger blocks light from the light emitter and the light receiver stops receiving the light, the presence of the passenger is thereby detected (see Patent Document 1).    Patent Document 1: JP 2003-341962 A